Generally, C.sub.5 aliphatic hydrocarbon resins are synthesized using a piperylene concentrate stream that has been fractionated to minimize levels of isoprene and cyclic diolefins such as cyclopentadiene and/or methylcyclopentadienes, as well as dimers and codimers of these compounds. The presence of these components in significant quantities (i.e. greater than 3 to about 5 percent) in polymerization feed blends is known to adversely affect the molecular weight and properties of the resin produced via cationic polymerization. For example, U.S. Pat. No. 2,750,353 discloses that high isoprene content (greater than 3.5 weight %) in the feedstock leads to inferior yields and gel formation. Likewise, U.S. Pat. No. 2,754,288 teaches that gel formation and poor molecular weight control result from the use of feeds that initially contain greater than 2 weight % cyclopentadiene. Isoprene and/or dicyclopentadienes have traditionally been considered undesirable at high concentrations in hydrocarbon resin feed blends targeted for catalytic polymerization due to their tendency to crosslink and form gels or resins of undesirably high molecular weight.
UK Patent Specification GB 1,408,870 (ICI), describes the heat soaking of a crude C.sub.5 stream followed by direct polymerization without fractionation. The patent uses an aluminum chloride complex and does not mention the incorporation of aromatic olefins.
UK Patent Specification 2,044,277A (Sumitomo), describes the copolymerization of cyclopentadiene with a copolymerizable monomer (chain conjugated diolefin or olefin) using an aluminum chloride/oxygen rich containing electron donor/aromatic solvent complex claiming no gel formation. Sumitomo teaches that aluminum chloride powder is not suitable for these type polymerizations and discloses the polymerization of feed blends containing cyclopentadiene:isoprene ratios of from 3:1 to 1:3. Further Sumitomo does not mention the incorporation of aromatic olefins.
U.S. Pat. No. 5,516,835, which discloses a tackifier comprising an isoprene based hydrocarbon resin obtained by the cationic polymerization (aluminum chloride) of a feed blend consisting of from 40-90 wt % isoprene and from 10-60 wt % of an aliphatic monoolefin (e.g., 2-methyl-2-butene).
U.S. Pat. No. 5,516,835 also discloses hot melt and pressure sensitive adhesive systems based on amorphous polypropylene, natural rubber and styrenated block copolymers. Further, the optional use of piperylenes, DCPD and aromatic olefins is disclosed.
U.S. Pat. No. 4,008,360 discloses resin produced from a C.sub.5 fraction that has been subjected to an adjustment of a weight ratio of acyclic diolefins to monooelfins and a weight ratio of cyclic diolefins to monoolefins of from 0.40 to 0.70 and from 0.07 to 0.35, respectively. The inclusion of aromatic olefins is not disclosed. Likewise, U.S. Pat. No. 4,952,639 discloses resins produced from a C.sub.5 fraction having aromatic mono-olefin and certain ratios of diolefins and mono-olefins, however dicyclopentadiene is absent.
Two other U.S. Patents. of interest are U.S. Pat. No. 3,950,453 (Nippon Zeon) and U.S. Pat. No. 3,467,632 (Reichold). Both of these patents disclose the cationic polymerization of feed blends containing up to 30 wt % isoprene, including the use of isoprene dimers (terpenes) as softening point boosters.
Hence, feedstocks with low levels of isoprene and dicyclopentadienes have been preferred in the industry. However, obtaining these feedstocks has required expensive purification procedures. Therefore, there is a need in the art to provide a method to polymerize the mix of isoprene cyclopentadiene/dicyclopentadienes, piperylene feedstocks into hydrocarbon resins without the undesirable gels or very high molecular weights.